1. Field of the Invention
The present invention relates to image deflection preventing devices used with cameras for preventing image deflection caused by camera movement resulting from such things as hand tremor and the like.
2. Description of the Related Art
In recent years, cameras have realized a marked increase in the use of electronics, including, but not limited to, the use of automatic exposure mechanisms and autofocus mechanisms. However, these technologies have been insufficient countermeasures against image deflection due to hand tremors and the like.
Because current technologies have been insufficient to deal with image deflection, various proposals have been made to prevent image deflection which arises from vibration of the camera and in particular from inclination of the camera. Such proposals have sought to correct for image deflection by detecting the vibration of the camera by means of angular velocity sensors. Moreover, these proposals have sought to prevent deflection by responding to the results of the angular velocity sensors by driving and shifting either the photographic lens system or the optical system of a portion of the photographic lens system. In cameras equipped with the aforementioned kind of image deflection preventing devices, the photographic lens system, or the optical system of a portion of the lens system is movably supported in a deflection preventing optical system and is moved in a plane which is orthogonal relative to the optical axis of the principal optical system and in a direction so as to absorb the deflection. In this manner, image deflection is minimized, but not eliminated. For a further description of devices of the type described above, reference is made to U.S. Pat. No. 5,084,724 to Maeno.
In spite of the aforementioned proposals to correct for image deflection, the above-mentioned systems maintain difficulties in accurately detecting the movement of a camera device. Moreover, angular velocity sensors, alone, do not account for the total correction of image deflection due to the many circumstances of camera vibration. In particular, a camera undergoes many complex motions during hand-held photography which can be classified as follows:
(1) Camera tilt motions (i.e., TILT of the optical axis of a camera's photographic lens); and PA1 (2) Camera shift motions which are approximately at right angles to the optical axis of the photographic lens system (i.e., SHIFT of the optical axis of a camera's photographic lens). PA1 a=The distance from the center point H of lens L to the photographic subject A; PA1 b=The distance from the center point H of lens L to the imaging plane B; PA1 f=The focal length of the lens L; PA1 .delta.1=The displacement of an image on the imaging plane B. PA1 .delta.1 is calculated according to the relationships among the following imaging equations: ##EQU1## and ##EQU2## and ##EQU3## .delta.1 will be realized in the direction of the arrow c in FIG. 19. PA1 .delta.2=m.gamma. ##EQU5##
As such, the vibrational effects of a camera device arise by the composition of the individual vibrational components due to the motions defined according to items (1) and (2) above. While the aforementioned image deflection preventing systems can detect camera vibration due to motion defined according to item (1), such image deflection preventing systems cannot detect camera device vibration due to motion defined according to item (2) above. Accordingly, the aforementioned image deflection preventing systems only allow for the prevention of deflection which occurs as a result of camera device motion defined by item (1) but not by motion defined by item (2).
To better understand the effects of the camera device vibrations defined in items (1) and (2) above, reference is now made to FIG. 18 which depicts a deflection situation. FIG. 18 shows a lens L which has been aligned along a center point of imaging plane B and which has realized a movement of its optical axis I to I' through an angle .THETA.. This kind of tilt of the optical axis I to I' results in a deflection of an image in accordance with the motion defined by item (1) above.
FIG. 19 illustrates the deflection realized due to the movement of the lens L's optical axis. When viewing the inclination of the optical axis I, with the principal point H of the lens L as center, the optical axis I similarly becomes tilted by an angle .THETA. to I". In order to fully analyze the effects of the deflection depicted in FIGS. 18 and 19 as a result of the motion defined in item (1) above, reference is now made to the following equations wherein the following variables bear the following meanings:
In assessing the deflection due to a shift of the principal point H of the lens L based on a motion defined by item (2) above, reference is now made to FIG. 20. By a tilt of the optical axis from I to I', the principal point H moves by .gamma. in the direction of the arrow d in FIG. 20. The deflection in the imaging plane is identified as .delta.2, and due to the photographic magnification m the following relationship emerges in view of equation 1 from above: ##EQU4##
Interestingly,
Finally, .delta.2 will be realized in the direction of the arrow c as depicted in FIG. 20.
With the foregoing formulae and relationships in mind, it should be understood that when the tilt of the optical axis from I to I' occurs as shown in FIG. 18, total deflection .delta. can be stated as: EQU .delta.=.delta.1+.delta.2 ##EQU6##
As noted above, the image deflection in the aforementioned devices is performed by angular velocity sensors. As such, the deflection .delta.1 due to the tilt of the optical axis from I to I' can be detected, but the deflection .delta.2 due to the shift of the principal point H of the lens L cannot be detected. Such a lack of detection of the motion defined by item (2) above is due to the fact that the movement .gamma. of the principal point H, which is not limited to the tilt of the camera normally around the image point B as the center, cannot be detected. In turn, the aforementioned image deflection detecting devices provide for the correction and adjustment of an optical system during motion defined by item (1) above.
Accordingly, it is desired to adopt some countermeasures capable of obtaining a deflection preventing function for the deflection .delta.2 which arises due to a shift of the principal point H of the above-mentioned lens L.